The correct answer is B) amount of dissolved gases.
Changes to air pressure affect the human body. These changes can happen when going into the depths of the ocean or when climbing mountain peaks. The increased pressure increases the body's amount of dissolved gases.
That is why it is so important to be in good health when you are about to be exposed to air pressure changes. Your body needs to be in good health, with the proper nutrition to resist these kinds of changes. That is how a mountain climber or alpinist needs to do a special preparation before climbing a mountain. The same happens when scuba diving.
